Absolute Power – More About Power Surges And Their Devastating Impact

By some estimates, power surges damage over 119000 desktop and laptop computers each year in just one state, Florida, in the USA.(1)

A power surge is a spike of energy in an electrical circuit. It’s an increase in voltage that significantly exceeds the standard 240volt flow of electricity. In technical terms, a surge is a transient wave of current or voltage in an electric circuit. In power systems, this refers to an overvoltage with duration of less than a half-cycle of the normal voltage waveform.

Power surges last fractions of a second, but they can cause a lot of damage. Like a jolt to the heart, a power surge carries thousands or tens of thousands of volts into the wiring system. It can crash computer hard drives, damage sensitive machinery, fry circuit boards, cause an explosion, and ruin electronic systems. The economic impact can be tremendous even from a single electrical surge.

Sources Of Surges

There are two types or sources of an electrical surge-

Internal Sources:

  1. Switching of electrical loads: The operation of certain electrical loads, whether done intended or unintended, can be a source of surges in the electrical system. These switching surges are disruptive and can damage equipment over time. These types occur as part of everyday operations. Sources of switching of electrical surges are fault clearing or interruption, power system recovery, starting and stopping of loads, fault or arc initiation, loose connections, etc.
  2. Magnetic and Inductive coupling: A magnetic field is created whenever an electric current flows. This magnetic field can easily extend itself to a second wire and induce a voltage in that wire. This voltage is transient in nature and is undesirable. Examples of equipment that can cause magnetic coupling are air conditioning systems, fluorescent light ballasts, elevators, heating ventilation, copy machines, and computers.
  3. Static electricity: An electrostatic discharge, or ESD, generates electromagnetic fields from a broad range of frequencies up to low gigahertz range. Electrostatic discharge results in a quick or sudden transfer of charge between bodies of differing electrostatic potentials. An electrostatic discharge can cause physical damage to equipment as well as equipment malfunction, and in extreme cases can even lead to the loss of life of personnel.

External Sources:

  1. Some external sources of surges are capacitor bank switching and utility-initiated. Under certain circumstances, like clearing a fallen tree branch or other accidents, the power utility may need to switch the power supply to another source or temporarily interrupt the flow of power. These interruptions of power cause surges when the power is disconnected from, and then reconnected to the customer loads.
  2. Lightning: The major external source of surges, and one that we will focus on more, is lightning. We know that lightning will take the path of least resistance and will discharge on conductive and elevated points such as trees, communications towers, tall buildings, and power lines. When lightning strikes a power line, the electricity spreads through the whole system causing a sudden spike in energy that can knock out transformers and can spread into your facility’s wiring system.

Types of current waves

  1. 10/350μsec current wave from direct lightning strikes (10μsec rise time and 350μsec is surge duration). Type 1 SPD characterized by 10/350μsec current wave.
  2. 8/20μ sec current wave from indirect lightning strikes (8μsec rise time and 20μsec is current surge duration). Type 2 SPD is characterized by 8/20 μsec.

Surge waveforms is key factor in selecting SPDs.

 

More about surges from Lightning

Direct & indirect type of lightning surge can damage electrical system and the connected loads.

1. Direct Lightning Strike-

A direct lightning strike can cause a significant amount of damage to the electrical and nonelectrical items in the system. In many cases, surges from direct lightning strike will start a fire, often in the wiring. It can also cause structural damage to the structure.

Types of direct lightning strikes-

  1. Lightening current directly strikes on a structure- Direct Lightning current of (10/350) waveform enters into a system where the structure receives a direct lightning strike.

  1. Lightning current flow when lightning strikes to a nearby service line. Direct Lightning current of (10/350) waveform strikes an overhead service line.

2. Indirect Lightning Strike-
An indirect lightning strike is the more common type, where a nearby lightning enters the system through wires or pipes that extend outside. This energy can travel through phone, internet, and cable wires directly from a utility pole into the electrical panel, or through conductive metal such as plumbing or metal bars in the foundation. Damage from this type of event is generally less severe as compared to a direct lightning strike.

Types of indirect lightning strikes-

  1. Lightning current flow when lightning strikes near the structure- Indirect lightning strikes near the structure represented by 8/20 current wave.

  1. Lightning current flow when lightning strikes near the structure- Indirect lightning strikes near the structure represented by 8/20 current wave.

Protection From Surges

It is extremely important to comprehensively protect your facility from lightning. A well-designed system of earthing and lightning protection is essential to help mitigate against a variety of risks and dangers associated with lightning strikes. This will also help address some of the risk posed by power surges caused by lightning.

An effective way of protection from an electrical surge is by using surge protectors or surge protection devices. Surge protectors or surge arresters protect power distribution and telecommunication systems from high voltage surges caused by lightning strikes. They intercept the current of the surge where they are installed and discharge them to earth, thus avoiding critical equipment. Surge arrestors also afford protection against overvoltage that can result from constant self-inducted and capacitive load switching. Surge protective devices have to play a twin role of protecting microprocessors against wear-and-tear and also from lightning.

It’s important to note that surge protectors are designed for specific voltage levels and circuit configurations. A surge current rating typically determines its level of protection. Simply having a surge protector won’t guarantee the safety of your equipment. You must keep in mind the size, usage, and type of your electrical equipment while setting up your surge protection system. The surge protection system must be strong enough to handle the regular surges and spikes in the application and should be placed in accordance with the relevant standards. Only surge protection that is properly sized and grounded will protect against damage.

Preventive and protective measures against surges are inexpensive and easy to deploy. As we have seen, power surges can happen at any time without a warning and can be caused by a lot of factors, whether internal or external. You’ve been warned – now it’s time to take the right preventive action!

Reference: https://www.bulldogadjusters.com/5-must-see-power-surge-statistics-florida-homeowner/

Publish Date : 03/02/2017